The present invention relates to a method for operating a hybrid drive device for a motor vehicle, and to a hybrid drive device.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
A hybrid drive device is used to drive a motor vehicle, and thus consequently to provide the torque for propelling the motor vehicle. The hybrid drive device includes hereby a plurality of drive units, in particular a plurality of drive units of varying types. One drive unit may be an engine, e.g. an internal combustion engine. Another example of a drive unit is an electric machine. The hybrid drive device is capable to provide the torque from only the engine or only from the electric machine, for example. At least temporarily, however, both these drive units may also be operatively connected to each other to provide the driving torque together.
The hybrid drive device has an output shaft which is operatively connected, rigidly and/or permanently, to wheels of the motor vehicle. A transmission is operatively connected, also rigidly and/or permanently, to the output shaft. A clutch may also be provided between the transmission and the output shaft, e.g. a starting clutch. As an alternative, the clutch or starting clutch may also be arranged between the transmission and the electric machine. A further clutch, in particular a separating clutch, may be arranged between the engine and the electric machine so as to be able to couple the engine to the electric machine. The engine may be permanently operatively connected to the electric machine.
During driving operation of the motor vehicle, both the engine and the electric machine are operatively connected to the output shaft of the transmission of the hybrid drive device, with both these drive units providing at least part of the driving torque. The electric machine can also be operated as a generator or dragged by the engine.
It would be desirable and advantageous to provide an improved method for operating a hybrid drive system for a motor vehicle to obviate prior art shortcomings and to provide a better thermal management of the electric machine while being reliable in operation.